A recently discovered asteroid is standing near our sun – much closer than our own planet Earth.
The asteroid, called 2021 PH27, orbits the sun every 113 days and approaches within 20 million kilometers of our star.
This gives this space rock the distinction of having the shortest known orbital period for an asteroid – and only the second shortest orbit around the sun after Mercury, which takes 88 days to complete its orbital journey around our star.
Scott Sheppard, an astronomer at the Carnegie Institution for Science, discovered the asteroid during twilight observations made by Brown University astronomers Ian Dell’Antonio and Shenming Fu on August 13.
Dell’Antonio, professor of physics, and Fu, doctoral student, took the images using the dark energy camera mounted on the four-meter Victor M. Blanco telescope at the Inter-American Observatory Cerro Tololo in Chile.
Several aspects of the asteroid surprised Sheppard.
The asteroid is 1 km long and “very few asteroids of this size in the inner solar system probably exist that are unknown,” he said.
“2021 PH27 gets so close to the sun that its surface can reach temperatures of 482 ° C, hot enough to melt lead,” Sheppard said via email. “Due to these extreme temperatures, the 2021 PH27 is unlikely to be made of a volatile material, and it is most likely made of rock with possibly a metal like iron.”
It has an unstable orbit that intersects the orbits of Mercury and Venus as they circle the sun. In a few million years, the asteroid’s orbit will likely cause its loss. The rock fragment could collide with Mercury or Venus, or the sun itself, or be knocked down from its current position in the solar system.
The asteroid is so close to the sun’s massive gravitational field that it experiences effects in its orbit, Sheppard said.
The new asteroid is just one of approximately 20 Atira asteroids, which are asteroids completely within the Earth’s orbit of the sun.
While there are a few known asteroids that approach almost as close to the sun as 2021 PH27, they have much longer orbits.
“Some of these asteroids have been seen with dust in their orbits, suggesting that the asteroids are slowly fragmenting or cracking apart from the extreme thermal stresses on these objects,” Sheppard said.
A notable example of this is Phaethon, the comet-like asteroid that creates the Geminid meteor showers that occur in our skies every December.
Track down an asteroid
But where does this space rock come from? This is one of the questions Sheppard wants to explore next, but he has some ideas based on the preliminary observations.
It’s likely that the asteroid has dislodged from the main asteroid belt between Mars and Jupiter, but Sheppard hasn’t ruled out the possibility that 2021 PH27 is in fact an extinct comet.
“It could be an extinct comet, as comets are known to come from the outer solar system in elongated, long-period orbits and gravitationally interact with inner planets to achieve more circular, shorter-period orbits that make them feel more circular. maintain in the inner solar system for long periods of time, ”explained Sheppard.
The inner planets include Mercury, Venus, Earth, and Mars.
When this happens, some elements of the comet evaporate until it no longer looks like a comet. Instead, it’s just the leftovers.
Sheppard typically searches for incredibly distant objects in the solar system and beyond. However, it is also crucial to understand the population of asteroids near Earth’s orbit. Near-Earth asteroids have a chance to impact Earth in the future, but some of them are incredibly difficult to observe as they approach our planet during the day.
“The interior of space in Earth’s orbit has been relatively unexplored to date,” Sheppard said. “It is difficult to observe the region towards the Sun because of the extreme glare of the Sun.”
But the Dark Energy Camera has a wide field of view, making it a powerful tool for searching for otherwise elusive objects like 2021 PH27 – especially during the twilight hours around sunset and just before it rises.
After Sheppard’s discovery, University of Hawaii astronomer David Tholen measured the asteroid’s position and predicted where it could be observed the following night. This allowed several telescopes to observe the asteroid from Chile and South Africa on August 14 and 15. These astronomers reported the sightings for their own research to help learn more about the asteroid.
“Although telescope time is very precious, the international nature and love of the unknown make astronomers very willing to bypass their own science and observations to follow exciting new discoveries like this,” Sheppard said. . “We are very grateful to all of our collaborators who allowed us to act quickly on this discovery.”
Soon the asteroid will pass behind the sun and will not be observable until early 2022. Sheppard is eager to learn more about the asteroid’s make-up and its origin.
“Where do these interior asteroids come from?” Some are recently dislodged Main Belt asteroids, others could be extinct comets, but there could be another source population, like the Vulcanoids, which is a hypothetical asteroid population, ”Sheppard said.